Lead Pollution in Ancient Rome May Have Dropped Average IQ by Up to 3 Points, Study Finds

Ice cores trap air bubbles and particles like dust, ash, and chemicals as snow falls and compresses over time. By extracting and analyzing these cores, scientists can study past atmospheric conditions, including temperature, greenhouse gases, and pollutants, providing a detailed climate history going back hundreds of thousands of years.

Lead pollution from Roman silver smelting was found in Greenland ice cores, showing its far-reaching impact.

• During smelting, lead mixed with atmospheric dust particles, which were later carried by wind and deposited in regions like Greenland.

Roman silver smelting was a major source of lead pollution. The Romans used silver for coinage, contributing heavily to atmospheric lead levels.

• For every ounce of silver produced, Romans emitted about 10,000 ounces of lead into the atmosphere.

Ice core data revealed that lead levels rose and fell in alignment with major Roman historical events, such as territorial expansion and increased silver production.

Lead pollution in ancient Rome likely reduced the population’s average IQ by 2.5 to 3 points.

Lead is a powerful neurotoxin that can cause learning disabilities, reproductive problems, mental health issues, and hearing loss, even at low exposure levels.

During the Pax Romana, a period of peace in the empire that lasted from 27 B.C.E. to A.D. 180, lead exposure levels were one-third of the U.S. levels during the peak of leaded gasoline use in the 1970s, and double the current levels for American children.

Roman-era lead pollution is the earliest clear evidence of large-scale industrial pollution affecting human health.

• The study marks the first clear example of industrial pollution with a continental-scale impact, predating modern pollution by 2,000 years.

Romans faced exposure not only from the atmosphere but also from lead-lined wine vessels, plumbing, and drinking goblets.

Roman silver smelting in Iberia (modern-day Spain) was a major contributor to lead pollution. The Romans mined and smelted silver extensively in the region, which led to high levels of lead being released into the atmosphere.

• People living near Roman silver mines in Iberia (modern-day Spain) likely had the highest levels of lead exposure in their blood.

Researchers believe lead exposure may have contributed to the fall of the Roman Empire, though it was likely just one of many factors.

Ancient Roman cities were plagued by poor sanitation, disease, and dysentery, with lead exposure adding to the health risks.

Romans had an average life expectancy of 25 to 30 years, with lead exposure worsening already harsh living conditions.